Reference GA embedding tuning SDK instead of preview

[skarukas]

Description

Fixes b/343522059

Reference GA embedding tuning SDK instead of preview. Also, add requirement numpy<2 to avoid ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject when running nox -s py-3.11.

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Checklist

• [x] I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• [x] README is updated to include all relevant information
• [x] Tests pass: nox -s py-3.11 (see Test Environment Setup)
• [x] Lint pass: nox -s lint (see Test Environment Setup)
• [ ] These samples need a new API enabled in testing projects to pass (let us know which ones)
• [ ] These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• [ ] This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• [ ] This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• [x] Please merge this PR for me once it is approved

[skarukas]

Looks like imagen/edit_image_inpainting_insert_mask_mode_test.py::test_edit_image_inpainting_insert_mask_mode is flaky due to 503 UNAVAILABLE. I don't think I have adequate permission to rerun the checks.